In modern web applications loading animations are an important part of the User Experience (UX). The User needs to know that something is going on – even if loading is usually very fast.
In early prototype development developers and product owners tend to omit any loading indicator. This is totally fine until first real users try the app. They may get confused and try to hit the refresh button or repeat button clicks. If a request is very fast, they might not notice that the content has changed and wait for something to happen.